The purpose of this investigation is to perform epidemiologic surveys and immunologic tests that will provide information concerning risk factors and will predict persons at risk for the Acquired Immune Deficiency Syndrome (AIDS). The populations under study are 1) asymptomatic homosexual men; 2) homosexual men with the chronic lymphadenopathy syndrome (CLS); 3) homosexual men with and without evidence of hepatitis B virus (HBV) infections; and 4) patients with hemophilia A. The initial studies will establish the incidence and prevalence of AIDS in Denver, Colorado, a community with a large homosexual population that does not yet have residents with AIDS. Subsequent serial studies will identify risk factors and establish the specificity and sensitivity of each immunologic test in the panel. Patients with hemophilia will clarify the role of blood borne transmissible agents in the pathogenesis of AIDS. The possible role of sperm in development of the immuno-deficiency in AIDS will be examined.